1. Field of the Invention
The present invention relates to a communication system. More particularly, the present invention relates to an apparatus and method for transmitting and receiving Connection Identifier (CID) information in a communication system.
2. Description of the Related Art
In a wireless communication system, a Mobile Station (MS) establishes a connection to a Base Station (BS) in order to communicate with the BS. The MS can establish multiple connections to the BS and is assigned multiple CIDs from the BS to respectively identify each of the multiple connections. The MS, when initially accessing a network of the communication system, is assigned a Basic CID and a Primary Management CID from the BS to transmit and receive control data or a control signal, to/from the BS. Further, the MS is assigned one or more Transport CID(s) for transmission/reception of user data.
Generally, the CID assigned from the BS to the MS has a unique value in the BS. Accordingly, if the MS moves from a service area of the BS to a service area of another BS, the MS should be assigned a new CID from the new BS. With reference to FIG. 1, a description will now be made of a transmission/reception operation for assigning Basic CID and Primary Management CID between a BS and an MS during handover of the MS.
FIG. 1 is a signaling diagram illustrating a method for transmitting and receiving CIDs in a conventional communication system.
Referring to FIG. 1, the communication system includes an MS 110, a first BS (BS1) 120, and a second BS (BS2) 130. In FIG. 1, the BS1 120 is assumed to be a serving BS which is providing a communication service to the MS 110, and the BS2 130 is assumed to be a target BS to which the MS 110 will handover.
The BS1 120 sends a Downlink Channel Descriptor (DCD) message to the MS 110 in step 111. More specifically, the DCD message is broadcast by the BS1 120 and received by the MS 110.
Upon receipt of the DCD message, the MS 110 sends a Ranging-Request (RNG-REQ) message to the BS1 120 in step 113. The RNG-REQ message includes basic information for establishing a call connection.
The BS1 120 sends a Ranging Response (RNG-RSP) message to the MS 110 in response to the RNG-REQ message in step 115. The RNG-RSP message includes a Basic CID assigned to the MS 110. It will be assumed in FIG. 1 that a Basic CID assigned to the MS 110 is, for example, ‘10’.
The MS 110 sends a Subscriber Station Basic Capability Request (SBC-REQ) message to the BS1 120 for basic capability negotiation for the MS 110 in step 117. The SBC-REQ message includes information on, for example, a modulation scheme and/or a coding scheme that the MS 110 can use.
Upon receipt of the SBC-REQ message from the MS 110, the BS1 120 sends a Subscriber Station Basic Capability Response (SBC-RSP) message to the MS 110 in response to the SBC-REQ message in step 119.
The MS 110 sends a Registration Request (REG-REQ) message to the BS1 120 in step 121. Upon receipt of the REG-REQ message, the BS1 120 registers the MS 110 using registration information of the MS 110, included in the REG-REQ message.
The BS1 120 sends a Registration Response (REG-RSP) message to the MS 110 in response to the REG-REQ message in step 123. The REG-RSP message includes registration information of the registered MS 110 and a Primary Management CID assigned to the MS 110. It will be assumed in FIG. 1 that a Primary Management CID assigned to the MS 110 is, for example, ‘110’.
Being assigned the Basic CID and Primary Management CID, the MS 110 sets up a connection to the BS1 120 using the Basic CID and Primary Management CID in step 125. The MS 110 can additionally be assigned a Transport CID(s) from the BS1 120, and can exchange user data with the BS1 120 using the Transport CID.
Upon detecting a need to handover, the MS 110 sends a Handover Request (HO-REQ) message to the BS1 120 in step 127.
Upon receipt of the HO-REQ message, the BS1 120 sends a Handover Response (HO-RSP) message to the MS 110 in response to the HO-REQ message in step 129. The HO-RSP message includes therein information on a target BS (e.g., BS2 130) to which the MS 110 will handover.
Upon receipt of the HO-RSP message, the MS 110 determines whether to handover to the BS2 130 using the information included in the HO-RSP message. The MS 110, when it determines to make a handover to the BS2 130, sends to the BS1 120 a Handover Indication (HO-IND) message indicating that it will soon handover to the BS2 130 in step 131.
After sending the HO-IND message to the BS1 120, the MS 110 sends a RNG-REQ message to the handover target BS, i.e., BS2 130 in step 133.
The BS2 130 sends a RNG-RSP message to the MS 110 in response to the RNG-REQ message in step 135. The RNG-RSP message includes Basic CID and Primary Management CID for CID update for the MS 110. It is assumed in FIG. 1 that a Basic CID assigned to the MS 110 is ‘30’, and a Primary Management CID assigned to the MS 110 is ‘130’.
Upon receiving the RNG-RSP message transmitted from the BS2 130, the MS 110 performs CID update using the CIDs included in the RNG-RSP message. The ‘CID update’ as used herein refers to an operation of replacing the Basic CID and Primary Management CID already assigned to the MS 110, with newly received Basic CID and Primary Management CID.
After performing the CID update, the MS 110 receives control data or control signals, transmitted from the BS2 130, and later on, the MS 110 is assigned a Transport CID from the BS2 130 and transmits user data to the BS2 130 using the Transport CID.
The CID, for example, the Basic CID, is a CID assigned from the BS for identification of each MS, and is uniquely assigned for each MS by each BS in whose service coverage area the MS is located.
As described above, since the CID is uniquely assigned to one MS by each BS, the MS must be reassigned a new CID when performing handover. Such reassignment requires resources of each BS. In addition, the procedure by which the MS is reassigned the new CID may suffer a time delay caused by the CID assignment thus potentially causing a degradation in service to the MS.